Detection of proteins at low concentrations is of paramount importance in the areas of medicine, food testing, biological research, and the detection of biowarfare agents. One of the most common tools for measuring proteins are antibodies, for example, immunoassays. One common alternative to using whole antibody molecules is to use just the binding regions of the antibody. For example, a variety of antigen-binding antibody fragments are known, such as Fab fragments, Fab′ fragments, F(ab)2 fragments, F(ab′)2 fragments, or scFv fragments.
Another recently alternative to antibodies for measuring target molecules are aptamers. Aptamers are nucleic acids molecules that can be obtained for use in measuring target molecules. Aptamers offer some advantages of being produced in vitro in a comparatively short time, of having a long shelf-life, being easy to modify chemically, and of potentially exhibiting better binding characteristics than antibodies but production of aptamers is high cost, and often stability is low in some biological fluids.
Present methods for detecting and/or determining the concentration of molecules in solution fail to combine short assay time, high sensitivity and ability to assay larger sample volumes required to detect and/or quantify target molecules present at very low concentration.